1. Field of the Invention
The present invention relates to an image carrier unit including a cleaning portion as well as to an image forming apparatus equipped with the unit.
2. Description of the Related Art
Various image forming apparatuses employ an electrophotography method to form a toner image on a sheet. In the electrophotography method, an exposure device irradiates an image forming surface of a photosensitive drum charged by a charger with light so as to form an electrostatic latent image. A developer supplies toner to the photosensitive drum, so that the toner adhering to the electrostatic latent image forms the toner image. The toner image is then transcribed and fixed onto the sheet. After the transcription of the toner image to the sheet, the image formation surface is cleaned, so that toner still remaining on the image formation surface is removed. After that a new toner image is formed on the image formation surface, and then transcribed and fixed onto a new sheet.
The toner removal is performed with a cleaning blade, for example, disposed downstream from a position where the toner image on the image formation surface is transcribed. The cleaning blade in contact with the image formation surface removes residual toner from the image formation surface. The toner removal with the cleaning blade may also be applied to the developer.
The cleaning blade typically includes a metal support and a rubber blade. A double-sided tape or an instant adhesive, for example, are used to fix the blade to the support. It may take a longer curing time to fix the blade to the support with the double-sided tape or the instant adhesive, and strength of the fixation between them has to be well controlled. Another method for fixing the blade to the support is thermal fusion. The fixation method with the thermal fusion, however, takes time for preheating process. Thus, no conventional fixation between the cleaning blade and the support is likely to contribute to reduction in a manufacturing cost because of a longer manufacturing time.
Screws and spacers may be used for fixing the blade to the support as yet another method, which may be likely to, however, increase a number of parts and require a larger space for accommodating the cleaning blade. Thus the method with the screws and the spacers is less likely to contribute to miniaturization.
Another drawback in the conventional toner removal process with the cleaning blade relates to removal of toner adhering to surfaces other than the image formation surface. In many cases, there are elongated strip regions, which are not subjected to the image formation process, adjacent to the image formation surface. In many cases, characteristics of toner adhering to the elongated strip regions are different from the residual toner adhering to the image formation surface. Therefore the conventional cleaning blade may not effectively remove the toner from the elongated strip regions.